In this paper,we investigate the complete convergence and complete moment conver-gence for weighted sums of arrays of rowwise asymptotically negatively associated(ANA)random variables,without assuming identical distri...In this paper,we investigate the complete convergence and complete moment conver-gence for weighted sums of arrays of rowwise asymptotically negatively associated(ANA)random variables,without assuming identical distribution.The obtained results not only extend those of An and Yuan[1]and Shen et al.[2]to the case of ANA random variables,but also partially improve them.展开更多
A new algorithm using orthogonal polynomials and sample moments was presented for estimating probability curves directly from experimental or field data of rock variables. The moments estimated directly from a sample ...A new algorithm using orthogonal polynomials and sample moments was presented for estimating probability curves directly from experimental or field data of rock variables. The moments estimated directly from a sample of observed values of a random variable could be conventional moments (moments about the origin or central moments) and probability-weighted moments (PWMs). Probability curves derived from orthogonal polynomials and conventional moments are probability density functions (PDF), and probability curves derived from orthogonal polynomials and PWMs are inverse cumulative density functions (CDF) of random variables. The proposed approach is verified by two most commonly-used theoretical standard distributions: normal and exponential distribution. Examples from observed data of uniaxial compressive strength of a rock and concrete strength data are presented for illustrative purposes. The results show that probability curves of rock variable can be accurately derived from orthogonal polynomials and sample moments. Orthogonal polynomials and PWMs enable more secure inferences to be made from relatively small samples about an underlying probability curve.展开更多
本文以小说Moment in Peking为例,运用费尔克劳的狭义互文性理论,探讨互文性在小说原文及汉语译文中的体现。Moment in Peking是用英文创作的中国题材的作品,即属于异语写作,其中包含的互文性更具复杂性,具体体现在原文互文的特殊性和...本文以小说Moment in Peking为例,运用费尔克劳的狭义互文性理论,探讨互文性在小说原文及汉语译文中的体现。Moment in Peking是用英文创作的中国题材的作品,即属于异语写作,其中包含的互文性更具复杂性,具体体现在原文互文的特殊性和翻译互文的特殊性两个方面。本文对费尔克劳划分的显性与成构互文性加以改造,使之更适合本个案的研究。本文通过分析认为,译者在语言文化转换过程中,尤其是在类似于本文个案的互文翻译过程中,应具有较强的读者转换意识;针对译入语读者,采用各种互文性翻译转换策略,保留、强化、淡化,甚至忽略原文的互文性,在整体上取得较好的读者阅读效果。展开更多
When calculating electromagnetic scattering using method of moments （MoM）, integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour...When calculating electromagnetic scattering using method of moments （MoM）, integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour integral. The integrand is expanded to Taylor series and the integral results in a closed form. The cut-off error is analyzed to show that the series converges fast and only about 2 terms can agree wel with the accurate result. The comparison of the perfect electric conductive （PEC） sphere＇s bi-static radar cross section （RCS） using MoM and the accurate method validates the feasibility in manipulating the singularity. The error due to the facet size and the cut-off terms of the series are analyzed in examples.展开更多
The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameter...The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameters and buried depth on rectification moment. It is hoped that the reference value of rectification moment can be offered to operator, and theoretical foundation can be laid for future automatic rectification technology. The results show that the rectification moment and angle generally exhibit good linear behavior in clay layers with different soil parameters or buried depths, and then the concept of rectification coefficient, that is, the ratio of rectification angle to rectification moment, is proposed; different soil parameters and buried depths have different influences on rectification coefficient, in which elastic modulus has great influence but others have little influences; the simulations of rectification process are preformed in clay layers with different elastic modulus, and fitting results show that elastic modulus and rectification coefficient present the quadratic function relation.展开更多
Dongjiahe Coal Mine belongs to the Carboniferous Permian coal field which has a high degree of karst and fissure development.This paper takes the working face of Dongjiahe Coal Mine as an example;through the microseis...Dongjiahe Coal Mine belongs to the Carboniferous Permian coal field which has a high degree of karst and fissure development.This paper takes the working face of Dongjiahe Coal Mine as an example;through the microseismic(MS)monitoring system arranged on the working face,the moment tensor theory was used to invert the focal mechanism solution of the anomalous area of the floor MS event;combining the numerical simulation and field data,the underlying floor faults were identified by the stress inversion method.The results show that:1)Moment tensors were decomposed into three components and the main type of rupture in this area is mixed failure according to the relative criterion;2)The hidden fault belongs to the reversed fault,its dip angle is approximately 70°,and the rupture length is 21 m determined by the inversion method of the initial dynamic polarity and stress in the focal mechanism;3)The failure process of the fault is divided into three stages by numerical simulation method combined with the temporal and spatial distribution of MS events.The results can provide a reference for early warning and evaluation of similar coal mine water inrush risks.展开更多
A novel method for estimation of an aerodynamic force and moment acting on an irregularly shaped body (such as HE projectile fragments) during its flight through the atmosphere is presented. The model assumes that fra...A novel method for estimation of an aerodynamic force and moment acting on an irregularly shaped body (such as HE projectile fragments) during its flight through the atmosphere is presented. The model assumes that fragments can be approximated with a tri-axial ellipsoid that has continuous surface given as a mathematical function. The model was validated with CFD data for a tri-axial ellipsoid and verified using CFD data on aerodynamic forces and moments acting on an irregularly shaped fragment. The contribution of this method is that it represents a significant step toward a modeling that does not require a cumbersome CFD simulation results for estimation of fragment dynamic and kinematic parameters. Due to this advantage, the model can predict the fragment motion consuming a negligible time when compared to the corresponding time consumed by CFD simulations. Parametric representation (generalization) of the fragment geometrical data and the conditions provides the way to analyze various correlations and how parameters influence the dynamics of the fragment flight.展开更多
Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived fr...Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived from an omnibus statistic involving the skewness and kurtosis of each component. The proposed criterion additionally provides a measurement for the model fit in an absolute sense. The performances of our criterion are satisfactory compared with other classical criteria through Monte-Carlo experiments.展开更多
With the increasing necessities for reliable printed circuit board(PCB) product, there has been a considerable demand for high speed and high precision vision positioning system. To locate a rectangular lead component...With the increasing necessities for reliable printed circuit board(PCB) product, there has been a considerable demand for high speed and high precision vision positioning system. To locate a rectangular lead component with high accuracy and reliability, a new visual positioning method was introduced. Considering the limitations of Ghosal sub-pixel edge detection algorithm, an improved algorithm was proposed, in which Harris corner features were used to coarsely detect the edge points and Zernike moments were adopted to accurately detect the edge points. Besides, two formulas were developed to determine the edge intersections whose sub-pixel coordinates were calculated with bilinear interpolation and conjugate gradient method. The last experimental results show that the proposed method can detect the deflection and offset, and the detection errors are less than 0.04° and 0.02 pixels.展开更多
One of the main challenges for multi-wheel hub motor driven vehicles is the coordination of individual drivetrains to improve mobility and stability in the steering process.This paper proposes a dual-steering mode bas...One of the main challenges for multi-wheel hub motor driven vehicles is the coordination of individual drivetrains to improve mobility and stability in the steering process.This paper proposes a dual-steering mode based on direct yaw moment control for enhancing vehicle steering ability in complex environ ments.The control system is designed as a hierarchical structure,with a yaw moment decision layer and a driving force distribution layer.In the higher-level layer,the objective optimization function is con-structed to obtain the slip steering ratio,which represents the degree of vehicle slip steering in the dual-steering mode.Ayaw moment controller using active disturbance rejection control theory is designed for continuous yaw rate control.When the actual yaw rate of the vehicle deviates from the reference yaw rate obtained by the vehicle reference model and the slip steering ratio,the yaw moment controller isactuated to determine the yaw moment demand for vehicle steering.In the lower-level layer,there is a torque distribution controller based on distribution rules,which meets the requirement of yaw moment demand without affecting the total longitudinal driving force of the vehicle.For verifying the validity and feasibility of the dual-steering mode,simulations were conducted on the hardware-in-loop real-time simulation platfomm.Additionally,corresponding real vehicle tests were carried out on an eight-wheel prototype vehicle.Test results were generally consistent with the simulation results,thereby demon-strating that the proposed dual-steering mode reduces steering radius and enhances the steering per-formance of the vehicle.展开更多
林语堂的第一部英文长篇小说Moment in Peking于1939年在美国出版,并大获成功。小说后被翻译为西班牙语、意大利语、德语、日语等,在中国也很快出现多种汉译本。本文旨在梳理该小说在中国的译介及读者的接受情况,并提出有必要对现有译...林语堂的第一部英文长篇小说Moment in Peking于1939年在美国出版,并大获成功。小说后被翻译为西班牙语、意大利语、德语、日语等,在中国也很快出现多种汉译本。本文旨在梳理该小说在中国的译介及读者的接受情况,并提出有必要对现有译本进行重新修订甚至重新翻译该小说乃至林语堂的其他英文著作。展开更多
For the system with the fuzzy failure state, the effects of the input random variables and the fuzzy failure state on the fuzzy probability of failure for the structural system are studied, and the moment-independence...For the system with the fuzzy failure state, the effects of the input random variables and the fuzzy failure state on the fuzzy probability of failure for the structural system are studied, and the moment-independence global sensitivity analysis（GSA） model is proposed to quantitatively measure these effects. According to the fuzzy random theory, the fuzzy failure state is transformed into an equivalent new random variable for the system, and the complementary function of the membership function of the fuzzy failure state is defined as the cumulative distribution function（CDF） of the new random variable. After introducing the new random variable, the equivalent performance function of the original problem is built. The difference between the unconditional fuzzy probability of failure and conditional fuzzy probability of failure is defined as the moment-independent GSA index. In order to solve the proposed GSA index efficiently, the Kriging-based algorithm is developed to estimate the defined moment-independence GSA index. Two engineering examples are employed to verify the feasibility and rationality of the presented GSA model, and the advantages of the developed Kriging method are also illustrated.展开更多
The goal of this study is to determine earthquake source processes of moderate to strong earthquakes in Western China using data recorded by the digital broadband stations in and near China. There are 12 broadband sta...The goal of this study is to determine earthquake source processes of moderate to strong earthquakes in Western China using data recorded by the digital broadband stations in and near China. There are 12 broadband stations on the Chinese mainland. This paper used a kind of moment tensor inversion method to study the large earthquakes in the Xizang (Tibet) region of China.In this study, we first ported and tested a moment\|tensor inversion code and then applied the technique to a large (magnitude M s=7.9) earthquake in Xizang region of China. The inversion for the earthquake moment tensor is performed in the frequency domain by fitting long\|period observed spectra to synthetic spectra calculated. For details of the method refer to Giardini and Beranzoli (1992). As part of the project, we extended the library of synthetics by including local (>100km) and teleseismic distances (2000km<distance<9000km) which allows now the use of data from additional stations. The Xizang region is one of the most unusual and spectacular topographic features on Earth rising, on average, more than 4000 meters above sea level. The high topography is the result of the collision between the Indian and Asian tectonic plates which is also the cause for the area’s high seismicity rate. As a preliminary study, the moment tensors were obtained for the large earthquake ( M s=7.9) of 8 Nov 1997 in Xizang region using data from five stations. The result is similar to the Harvard CMT solution; for strike, dip and rake, this paper obtained 343, 76 and -177 degrees, respectively, while the Harvard CMT values are 348, 88 and 159. The moment magnitude estimate of Harvard is only 0.1 unit larger than my estimate of M w=7 4.. The fit in the frequency domain (phase and amplitude) suggests the reasonable result. At long periods the earthquake depth is generally not well resolved. Inversions for several trial depths, however, show a clear variance minimum for centroid depths (the average depth over the entire rupture plane) of a little less than about 12km. This is roughly consistent with the Harvard estimate of 16.4km. The fit result also shows that the fault plane solution is stable and well resolved. The test of the frequence band influence suggests that for each band the results are stable over a wide depth range. However, the results at one trial depth slightly depend on the frequency band. This research is being performed still, due to the important implication of Xizang region on geodynamics studies. Combining with more data, geological investigation and stress field analysis, we will give further results and discussion.展开更多
With photoelectric tracking system as the research object,based on the theorem of moment of momentum and Euler dynamic equation,Nonlinear biaxial coupling dynamic model of tracking turntable is established.Effects of ...With photoelectric tracking system as the research object,based on the theorem of moment of momentum and Euler dynamic equation,Nonlinear biaxial coupling dynamic model of tracking turntable is established.Effects of moment of inertia coupling,speed coupling and the dynamic coupling between tracking turntable shafts were studied,the analytical relation between them was given in theory.Verify the change trend of theoretical model.And it provides the theory reference and model base,for the future design of the high precision tracking controller And control parameter selection and optimization.In the end,specific measures are made for structure optimization.展开更多
In this paper, with the Kronecker's product and Kronecker's sum of matrices, the 2nd order moment equations of linear Ito stochastic systems are dervided. Based on the moment equations obtained, a necessary an...In this paper, with the Kronecker's product and Kronecker's sum of matrices, the 2nd order moment equations of linear Ito stochastic systems are dervided. Based on the moment equations obtained, a necessary and sufficient condition for the mean-square asymptotic stability of linear Ito stochastic systems is obtained.For the time-invariant stochastic systems,the necessary and sufficient condition is just the same as the Hurwitz property of certain matrices related to the coefficient matrices of the systems. An algorithm STILSS is given for testing the mean-square asymptotic stability of time-invariant linear Ito stochastic systems.展开更多
Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are ess...Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.展开更多
The foreign experimental and FEM research of steel moment-resisting connection reinforced with steel plates are introduced. The effect of weld on the connection design is studied in two ways including weld detail and ...The foreign experimental and FEM research of steel moment-resisting connection reinforced with steel plates are introduced. The effect of weld on the connection design is studied in two ways including weld detail and geometrical detail of steel plates contrast to the reference drawing of connection design in China. The research shows that the weld plays an important role in the design of connections. The welds connecting reinforced plates and beam/column flange and the plate geometry have direct influence on the performance of the connections reinforced with plates. The study is helpful to the application of design of steel moment-resisting connection with steel plates.展开更多
基金National Natural Science Foundation of China (Grant Nos.12061028, 71871046)Support Program of the Guangxi China Science Foundation (Grant No.2018GXNSFAA281011)。
文摘In this paper,we investigate the complete convergence and complete moment conver-gence for weighted sums of arrays of rowwise asymptotically negatively associated(ANA)random variables,without assuming identical distribution.The obtained results not only extend those of An and Yuan[1]and Shen et al.[2]to the case of ANA random variables,but also partially improve them.
文摘A new algorithm using orthogonal polynomials and sample moments was presented for estimating probability curves directly from experimental or field data of rock variables. The moments estimated directly from a sample of observed values of a random variable could be conventional moments (moments about the origin or central moments) and probability-weighted moments (PWMs). Probability curves derived from orthogonal polynomials and conventional moments are probability density functions (PDF), and probability curves derived from orthogonal polynomials and PWMs are inverse cumulative density functions (CDF) of random variables. The proposed approach is verified by two most commonly-used theoretical standard distributions: normal and exponential distribution. Examples from observed data of uniaxial compressive strength of a rock and concrete strength data are presented for illustrative purposes. The results show that probability curves of rock variable can be accurately derived from orthogonal polynomials and sample moments. Orthogonal polynomials and PWMs enable more secure inferences to be made from relatively small samples about an underlying probability curve.
文摘本文以小说Moment in Peking为例,运用费尔克劳的狭义互文性理论,探讨互文性在小说原文及汉语译文中的体现。Moment in Peking是用英文创作的中国题材的作品,即属于异语写作,其中包含的互文性更具复杂性,具体体现在原文互文的特殊性和翻译互文的特殊性两个方面。本文对费尔克劳划分的显性与成构互文性加以改造,使之更适合本个案的研究。本文通过分析认为,译者在语言文化转换过程中,尤其是在类似于本文个案的互文翻译过程中,应具有较强的读者转换意识;针对译入语读者,采用各种互文性翻译转换策略,保留、强化、淡化,甚至忽略原文的互文性,在整体上取得较好的读者阅读效果。
基金supported by the National Natural Science Foundationof China for the Youth(51307004)
文摘When calculating electromagnetic scattering using method of moments （MoM）, integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour integral. The integrand is expanded to Taylor series and the integral results in a closed form. The cut-off error is analyzed to show that the series converges fast and only about 2 terms can agree wel with the accurate result. The comparison of the perfect electric conductive （PEC） sphere＇s bi-static radar cross section （RCS） using MoM and the accurate method validates the feasibility in manipulating the singularity. The error due to the facet size and the cut-off terms of the series are analyzed in examples.
基金Project(2007CB714006)supported by the National Basic Research Program of China
文摘The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameters and buried depth on rectification moment. It is hoped that the reference value of rectification moment can be offered to operator, and theoretical foundation can be laid for future automatic rectification technology. The results show that the rectification moment and angle generally exhibit good linear behavior in clay layers with different soil parameters or buried depths, and then the concept of rectification coefficient, that is, the ratio of rectification angle to rectification moment, is proposed; different soil parameters and buried depths have different influences on rectification coefficient, in which elastic modulus has great influence but others have little influences; the simulations of rectification process are preformed in clay layers with different elastic modulus, and fitting results show that elastic modulus and rectification coefficient present the quadratic function relation.
基金Project(2017YFC1503103)supported by the National Key Research and Development Plan of ChinaProjects(51774064,51974055,41941018)supported by the National Natural Science Foundation of China+1 种基金Project(DUT20GJ216)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(51627804)supported by the Special-Funded Program on National Key Scientific Instruments and Equipment Development,China。
文摘Dongjiahe Coal Mine belongs to the Carboniferous Permian coal field which has a high degree of karst and fissure development.This paper takes the working face of Dongjiahe Coal Mine as an example;through the microseismic(MS)monitoring system arranged on the working face,the moment tensor theory was used to invert the focal mechanism solution of the anomalous area of the floor MS event;combining the numerical simulation and field data,the underlying floor faults were identified by the stress inversion method.The results show that:1)Moment tensors were decomposed into three components and the main type of rupture in this area is mixed failure according to the relative criterion;2)The hidden fault belongs to the reversed fault,its dip angle is approximately 70°,and the rupture length is 21 m determined by the inversion method of the initial dynamic polarity and stress in the focal mechanism;3)The failure process of the fault is divided into three stages by numerical simulation method combined with the temporal and spatial distribution of MS events.The results can provide a reference for early warning and evaluation of similar coal mine water inrush risks.
文摘A novel method for estimation of an aerodynamic force and moment acting on an irregularly shaped body (such as HE projectile fragments) during its flight through the atmosphere is presented. The model assumes that fragments can be approximated with a tri-axial ellipsoid that has continuous surface given as a mathematical function. The model was validated with CFD data for a tri-axial ellipsoid and verified using CFD data on aerodynamic forces and moments acting on an irregularly shaped fragment. The contribution of this method is that it represents a significant step toward a modeling that does not require a cumbersome CFD simulation results for estimation of fragment dynamic and kinematic parameters. Due to this advantage, the model can predict the fragment motion consuming a negligible time when compared to the corresponding time consumed by CFD simulations. Parametric representation (generalization) of the fragment geometrical data and the conditions provides the way to analyze various correlations and how parameters influence the dynamics of the fragment flight.
基金supported by the National Natural Sciences Foundation of China(7137102271401193+2 种基金71671193)the Program for Innovation Research in Central University of Finance and Economicsthe Innovation Foundation of BUAA for Ph.D.Graduates
文摘Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived from an omnibus statistic involving the skewness and kurtosis of each component. The proposed criterion additionally provides a measurement for the model fit in an absolute sense. The performances of our criterion are satisfactory compared with other classical criteria through Monte-Carlo experiments.
基金Project(51175242)supported by the National Natural Science Foundation of ChinaProject(BA2012031)supported by the Jiangsu Province Science and Technology Foundation of China
文摘With the increasing necessities for reliable printed circuit board(PCB) product, there has been a considerable demand for high speed and high precision vision positioning system. To locate a rectangular lead component with high accuracy and reliability, a new visual positioning method was introduced. Considering the limitations of Ghosal sub-pixel edge detection algorithm, an improved algorithm was proposed, in which Harris corner features were used to coarsely detect the edge points and Zernike moments were adopted to accurately detect the edge points. Besides, two formulas were developed to determine the edge intersections whose sub-pixel coordinates were calculated with bilinear interpolation and conjugate gradient method. The last experimental results show that the proposed method can detect the deflection and offset, and the detection errors are less than 0.04° and 0.02 pixels.
基金This work was supported by the Weapons and Equipment Pre-Research Project of China(No.301051102).
文摘One of the main challenges for multi-wheel hub motor driven vehicles is the coordination of individual drivetrains to improve mobility and stability in the steering process.This paper proposes a dual-steering mode based on direct yaw moment control for enhancing vehicle steering ability in complex environ ments.The control system is designed as a hierarchical structure,with a yaw moment decision layer and a driving force distribution layer.In the higher-level layer,the objective optimization function is con-structed to obtain the slip steering ratio,which represents the degree of vehicle slip steering in the dual-steering mode.Ayaw moment controller using active disturbance rejection control theory is designed for continuous yaw rate control.When the actual yaw rate of the vehicle deviates from the reference yaw rate obtained by the vehicle reference model and the slip steering ratio,the yaw moment controller isactuated to determine the yaw moment demand for vehicle steering.In the lower-level layer,there is a torque distribution controller based on distribution rules,which meets the requirement of yaw moment demand without affecting the total longitudinal driving force of the vehicle.For verifying the validity and feasibility of the dual-steering mode,simulations were conducted on the hardware-in-loop real-time simulation platfomm.Additionally,corresponding real vehicle tests were carried out on an eight-wheel prototype vehicle.Test results were generally consistent with the simulation results,thereby demon-strating that the proposed dual-steering mode reduces steering radius and enhances the steering per-formance of the vehicle.
基金supported by the National Natural Science Foundation of China(11702281)the Science Challenge Project(TZ2018007)the Technology Foundation Project of State Administration of Science,Technology and Industry for National Defence,PRC(JSZL2017212A001)
文摘For the system with the fuzzy failure state, the effects of the input random variables and the fuzzy failure state on the fuzzy probability of failure for the structural system are studied, and the moment-independence global sensitivity analysis（GSA） model is proposed to quantitatively measure these effects. According to the fuzzy random theory, the fuzzy failure state is transformed into an equivalent new random variable for the system, and the complementary function of the membership function of the fuzzy failure state is defined as the cumulative distribution function（CDF） of the new random variable. After introducing the new random variable, the equivalent performance function of the original problem is built. The difference between the unconditional fuzzy probability of failure and conditional fuzzy probability of failure is defined as the moment-independent GSA index. In order to solve the proposed GSA index efficiently, the Kriging-based algorithm is developed to estimate the defined moment-independence GSA index. Two engineering examples are employed to verify the feasibility and rationality of the presented GSA model, and the advantages of the developed Kriging method are also illustrated.
文摘The goal of this study is to determine earthquake source processes of moderate to strong earthquakes in Western China using data recorded by the digital broadband stations in and near China. There are 12 broadband stations on the Chinese mainland. This paper used a kind of moment tensor inversion method to study the large earthquakes in the Xizang (Tibet) region of China.In this study, we first ported and tested a moment\|tensor inversion code and then applied the technique to a large (magnitude M s=7.9) earthquake in Xizang region of China. The inversion for the earthquake moment tensor is performed in the frequency domain by fitting long\|period observed spectra to synthetic spectra calculated. For details of the method refer to Giardini and Beranzoli (1992). As part of the project, we extended the library of synthetics by including local (>100km) and teleseismic distances (2000km<distance<9000km) which allows now the use of data from additional stations. The Xizang region is one of the most unusual and spectacular topographic features on Earth rising, on average, more than 4000 meters above sea level. The high topography is the result of the collision between the Indian and Asian tectonic plates which is also the cause for the area’s high seismicity rate. As a preliminary study, the moment tensors were obtained for the large earthquake ( M s=7.9) of 8 Nov 1997 in Xizang region using data from five stations. The result is similar to the Harvard CMT solution; for strike, dip and rake, this paper obtained 343, 76 and -177 degrees, respectively, while the Harvard CMT values are 348, 88 and 159. The moment magnitude estimate of Harvard is only 0.1 unit larger than my estimate of M w=7 4.. The fit in the frequency domain (phase and amplitude) suggests the reasonable result. At long periods the earthquake depth is generally not well resolved. Inversions for several trial depths, however, show a clear variance minimum for centroid depths (the average depth over the entire rupture plane) of a little less than about 12km. This is roughly consistent with the Harvard estimate of 16.4km. The fit result also shows that the fault plane solution is stable and well resolved. The test of the frequence band influence suggests that for each band the results are stable over a wide depth range. However, the results at one trial depth slightly depend on the frequency band. This research is being performed still, due to the important implication of Xizang region on geodynamics studies. Combining with more data, geological investigation and stress field analysis, we will give further results and discussion.
文摘With photoelectric tracking system as the research object,based on the theorem of moment of momentum and Euler dynamic equation,Nonlinear biaxial coupling dynamic model of tracking turntable is established.Effects of moment of inertia coupling,speed coupling and the dynamic coupling between tracking turntable shafts were studied,the analytical relation between them was given in theory.Verify the change trend of theoretical model.And it provides the theory reference and model base,for the future design of the high precision tracking controller And control parameter selection and optimization.In the end,specific measures are made for structure optimization.
文摘In this paper, with the Kronecker's product and Kronecker's sum of matrices, the 2nd order moment equations of linear Ito stochastic systems are dervided. Based on the moment equations obtained, a necessary and sufficient condition for the mean-square asymptotic stability of linear Ito stochastic systems is obtained.For the time-invariant stochastic systems,the necessary and sufficient condition is just the same as the Hurwitz property of certain matrices related to the coefficient matrices of the systems. An algorithm STILSS is given for testing the mean-square asymptotic stability of time-invariant linear Ito stochastic systems.
基金Projects(U1934207,52078487,51778630) supported by the National Natural Science Foundations of ChinaProject(502501006) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2019RS3009) supported by the Hunan Innovative Provincial Construction Project,China。
文摘Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.
文摘The foreign experimental and FEM research of steel moment-resisting connection reinforced with steel plates are introduced. The effect of weld on the connection design is studied in two ways including weld detail and geometrical detail of steel plates contrast to the reference drawing of connection design in China. The research shows that the weld plays an important role in the design of connections. The welds connecting reinforced plates and beam/column flange and the plate geometry have direct influence on the performance of the connections reinforced with plates. The study is helpful to the application of design of steel moment-resisting connection with steel plates.
